Lots of questions.

> So if i install a 7000rpm racing camshaft would it achieve a higher top seed?

Probably not. The camshaft only works effectively in combination with other parts. With an Engine buildup it will work.


> Also, what is the 3.700 final gear that you mentioned?

The differential ring & pinion (crown wheel & pinion) gear.


> I will probably put on wider tyres on it, and maybe slightly shorter tyres. Will this have a great effect on top speed?

The width of tyre has no effect on top speed. However changing the diameter of tire is the same as changing the gear ratio. Bottom line is that a stock A15 only makes enough HP to power the car to go approximately 100mph/160kph. So gearing or tyre speed cannot raise the top speed. You need more HP to go faster.